Method for producing highly mechanically demanded pieces and specially tools from low cost ceramics or polymers

ABSTRACT

The present invention is directed to a method for the production of highly demanded pieces at low cost. The method is especially well suited for deep drawing dies, but also any other type of tooling. It is also very well suited for machine components of big dimensions and with high mechanical solicitations, like rotors and cages in wind mills and other big machines. The pieces or tools are cast with a low cost ceramic, like a high resistance concrete (with special mention to HPC or UHPC) or a low water admixture castable or any other low cost high mechanical resistance material (low cost ceramics or high resistance polymers are especially suited). Once cast, the working surface of the die or piece is coated with a metal, an intermetallic or a high performance ceramic. Projection or deposition techniques are used to obtain the high value working surface.

FIELD OF THE INVENTION

The present invention is directed to a method to fabricate highlysolicited pieces, and especially well suited for tools and dies, bycasting a low cost high resistance base material (like high andultra-high resistance concretes [UPC, UHPC], high resistance low wateradmixture castables or high resistance thermo-setting polymers) to thedesired shape, and then at least partially coating the surface with ametal or a technical ceramic. Usually projection or depositiontechniques can be employed to provide the metallic layer like coldspraying, CVD, PVD, or thermal spray techniques like arc, plasma, laser,oxi-fuel . . . . The metallic layer can also be partially or completelymelted and/or shot blasted. Technological ceramics can also be projectedor deposited. Metallic liners or rings can be used in the case ofrevolution figures.

BACKGROUND OF THE INVENTION

Nowadays, techniques for the construction of concrete tools exist, asfor instance in U.S. Pat. No. 4,588,443. However, these methods cannotbe applied to sheet drawing or other highly demanded applications as themechanical resistance is lacking, because the resistance of the usedconcretes or metal layers in the working zones is too low. There arealso techniques to obtain reinforced polymeric concretes of highresistance (GB2250703A), reinforced concretes with fibres for theconstruction of injection moulds (JP2003170410) or the application ofreinforced highly resistant polymers (WO 03/039779 A1). However, in allthese cases the possibility of using these techniques for shaping highquality sheets and other metal to metal contact applications is verysmall. The elements which are used to reinforce the concrete or polymerscratch the drawn sheet, and the superficial microdefects permit thedeposit of sheet particles which in turn produce adherences in sheetswhich will be drawn afterwards. In order to avoid this effect, sometechniques were developed by surface melting of a metallic layer(DE69908273T2) or by employing a layer which can be used as mould forthe concrete mix (JP2002346663, DE202006010493U1).

In both cases, the quality of the union metal-concrete is onlysatisfactory for few applications.

The use of concrete as support element and not as principal resistantelement (as it is the case in the present invention) in the producedpieces by thermal projection of metals is known. Normally, thesetechniques in which the concrete is used as support element, theconcrete is cast in the metallic piece once it is obtained by thermalprojection on another model (JP63309332, U.S. Pat. No. 3,631,745,JP2104424, JP2251323).

Realising thermal projection on concrete when the concrete is theresistant element is also known in protecting concrete against corrosionor against fire as it is described in U.S. Pat. No. 6,224,943, EP0669299A2, and U.S. Pat. No. 5,879,817. Thermal projection on low resistanceresins is also known in the production of low cost models where themechanical requirements are low (JP60108122).

There are many techniques for inserting layers by thermal projectionwhich are wear or corrosion resistant in comparison to the metallicsubstrates, in particular, ceramics and hard metals (JP2004175112).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plot of normalized shaping time.

FIG. 2 is a schematic representation of a drawing die.

DETAILED DESCRIPTION OF THE INVENTION

In the sheet processing industry, the tool costs represent in general animportant part of the costs of the produced pieces. For that reason, thefabrication of low cost tools is very interesting, in particular, assome of these tools do not need to have a very long life cycle.

In many other industries the usage of big structural or machinecomponents represent a high cost, especially when those elements arehighly solicited and expensive cast metals or even forged metal have tobe employed to withstand the high involved loads. This is often the casein energy transforming machines and processing machines.

The majority of the tools which are used to shape sheets aremanufactured by casting iron alloys and subsequent final machining ofthe desired geometry. They are also produced starting from metallicblocks which are machined until they have got the desired geometry.However, this normally implies the removal of great amounts of materialby machining.

The present invention is especially advantageously for manufacturinghuge deep drawing dies. Generally, deep drawing dies are manufactured bycasting steel according to the following process:

obtaining models (the most commonly employed material is expandedpolystyrene, but others can be used too, in particular, when the finalmachining shall be minimized, since the dimensional stability ofexpanded polystyrene is low)

obtaining sand moulds which are put around the model

casting the melt steel mix in the sand mould (the melt itself eliminatesthe model, in the case of not using polystyrene the model can previouslybe taken away and the melt can be casted in the hollow cavern)

taking away the mould and cleaning the melt

heat treating of the melt—optional

final machining

final heat treatments

In some cases and, above all, if there is big time pressure and if thetool is intended for the production of small series, the die ismanufactured by chip removal machining from a metallic block which iseasy to machine and which commonly is made of an aluminium alloy or alow alloyed steel.

The properties which the finished deep drawing die needs to have are:

dimensional stability in order to guarantee that the desired piece willbe obtained. This implies that the employed material needs to havesufficient mechanical resistance. The aluminium that is commonly usedfor that purpose has normally a resistance of 300 MPa, and the steelscommonly used normally have a mechanical resistance of more than 400MPa.

toughness in order to guarantee that the tool does not break. That's themean reason metals are used.

wear resistance in order to guarantee that the obtained geometry of thepiece will not significantly change during the tool's life. This isbasically the reason why different materials are used depending on therequired tool life and the shaped sheet type.

surface condition in order to guarantee a good surface quality of theproduced piece. The tool should not scratch the produced component.Scratches can be caused by the presence of very abrasive and bigparticles in the tool material which are surrounded by a far moredeformable or degradable matrix. This increments the contact pressure asthe area of real contact is drastically reduced. Scratches or marks onthe piece can also be caused by adherences if there is an affinitybetween the piece's material and the tool. Or they can be caused byholes or surface defects on the tool in which may deposit some piece'smaterial which in turn has a high affinity with subsequent processedpieces.

A fifth requirement could be also considered: namely the necessity ofobtaining pieces with elevated dimensional tolerances. This is to saythat the tool needs to have a high dimensional accuracy and stability.

All of the above requirements or at least some of them are shared bymany other applications, and thus the solution presented in the presentinvention can be applied. This is the case of many structural and activeparts in machines. In the case of big machine parts the economicadvantage of applying the present method is even bigger. Cages, axis,rotors, rolls, sliding contacts, motor blocks, machine benches and manyothers are candidates to the applying of the present invention.

Furthermore, the present invention allows providing the produced piecewith very diverse surface or subsurface functionalities like: heating,cooling, sensory, actuator, conducting or inducting in almost anypossible desired pattern. This is extremely interesting for aninnumerable range of applications, to serve as an example: Inductors,stators, hot forming cooled prototype dies . . . .

Given the requirements of the tools, the present invention provides amethod of obtaining highly solicited pieces, particularly advantageousfor tools like big deep drawing dies, with the required characteristicsand at considerably lower costs by constructing the objective piece witha low cost base material and with a surface layer which is made of amore expensive material and which provide the necessary properties whichwere described in the previous paragraphs. The layer is normally addedby a thermal projection or deposition technique. Usually, the addedlayer is of a metallic nature, very often steel. However, in the case ofpieces which need to have a high wear resistance or electric or thermalinsulation effect, the layer can also be a technical ceramic, finallythe superficial layer can also be an intermetallic compound or acomposite encompassing any of the three materials families described(metals, intermetallics and technical ceramics). In the case ofpiezoelectric, piroelectric, strong magnetic or other sensor or actuatoreffects, normally ceramics with the desired properties are projectedoften in combination with a metallic support layer. In the case ofdetermined thermal or electric conduction paths in the surface of theproduced piece, materials with different corresponding property (thermalor electric conductivity or magnetic permeability mainly) are projectedin the desired form trough proper masking.

Accordingly, a first aspect of the invention relates to a piece or toolcomprising a ceramic or polymeric base material having a mechanicalresistance higher than 60 MPa which is at least partially coated with ametal, an intermetallic compound or a technical ceramic.

A second aspect of the invention relates to a method for themanufacturing of pieces or tools comprising the following steps:

-   -   a) casting a ceramic or polymeric base material having a        mechanical resistance higher than 60 MPa into the desired shape;    -   b) allowing the cited base material to at least partially        solidify or harden; and    -   c) at least partially coating the surface of the piece resulting        from step b) with a metal, an intermetallic compound or a        technical ceramic.

Embodiments of the present invention are described below, by way ofexamples only:

In the present invention, the low cost base material employed is usuallya concrete or a low water admixture castable. A high resistance thermosetting polymer might also be used, although it is a bit less suited.Alternatively, a polymer of high resistance or any low cost ceramic,with sufficient mechanical properties, can be used. The requiredresistance level of the support base material depends on the sheet whichhas to be shaped (on its mechanical resistance, thickness and drawinggeometry) and, above all, on the thickness of the employed surfacelayer. For huge dies for skin production in the automotive industry,sheets of high ability for drawing with a mechanical resistance of about240 MPa and an elastic limit of about 200 MPa are used. In the image 1can be seen that for a drawing geometry with quite acute angles asurface resistance of more than 200 MPa may be required, but only 0.5 mmaway from the surface the required resistance is lower than 150 MPa.There are many low cost materials with a compression resistance higherthan 100 MPa, in particular, concretes and thermo stables. Conventionalconcretes on the basis of porcelain (porcelainates) with the addition offluxing agent and/or silica can achieve resistances of 140 MPa. Thereare polymeric cements with a resistance of more than 120 MPa. Premixedconcretes on the basis of low humidification cements and fibrereinforcement (“low water admixture castables”) can reach resistances ofmore than 250 MPa. Also thermosetting polymers with a resistance of morethan 300 MPa can be used as a base material or to partially replace theceramic. This polymer base materials are also very good candidates tofill up the superficial voids that can remain during the casting of thebase material especially if those voids are detrimental for theapplication of the metallic or technological ceramic layer. If the usedthermo projection process exposes the basis to a high temperature or ifthe final application requires particular resistances at a particulartemperature, refractory concretes on the basis of aluminates or lowwater admixture cements on the basis of alumina can be employed. Thecharacteristics of many of these concretes can be substantially improvedif an internal and/or external vibrator is used during the mixingprocess. Some of these low cost materials with a higher resistance needa high energy input mixing. Some of these materials need an agingprocess which may require their exposition to high temperatures. Othermaterials, which can be used for particular applications, arecompositions of a polymeric die with a metallic or ceramicreinforcement, also reinforcements of low cost ceramics, or arecompositions of a ceramic die with a metallic or polymericreinforcement.

In some instances of the present invention it is interesting that thelow cost base material has a mechanical resistance as high as possible.This is for example the case of many of the machine elements and alsothe case when using the present invention to fabricate tools to shapevery hard AHSS sheets. In this case extreme high resistance concretescan be used. Several tricks can be employed to raise the already highmechanical resistance of high resistance concretes (HPC) like forexample: the application of a pressure step to the piece right aftercasting it to suddenly evacuate some water of the mix, required to letthe concrete flow during the filling, but not desirable during thesetting of the concrete (it might require a special mould construction),in this way mechanical resistances above 400 MPa are attainable; usageof metallic balls or aggregates (can also be coated) to replace some ofthe arid, in this way mechanical resistances above 1000 MPa areattainable; usage of nanometric metallic powder (can also be coated) topartially replace cement, in this way mechanical resistances above 1300MPa are attainable, the preceding strategies can also be combinedtogether. When the tensile strength of the base material is also ofsignificance, the usage of metallic fibres (different natures andlengths), polymeric or textile fibres and other reinforcements can bevery advantageous.

In some instances of the present invention it is appreciated the lowweight of the components that can be attained. To further enhance thischaracteristic, the weight of the base material can be lowered byintentionally leaving voids in the low cost base material, or mixinginto the mix before casting some low weight material. An illustrativeexample of this practice would be the addition of expanded polyesthirenein the shape of balls or chuncks of the desired size, after the castingof the ceramic this added material can be eliminated to leave voids onthe concrete (material can be eliminated with temperature, acid, anyother mean) or simply be left in place. Other eliminable materials canbe employed if voids are desirable, or low weight material to be left inthe base material like such as low density polymer, cellulose, wax, inballs or particles. The voids in the base material can also be left byblowing a gas during the filling of the mould.

For the fabrication of the mould, which contains the extreme highresistance concrete or other low cost material of extreme highresistance in order to give it the desired geometry, in general,expanded polystyrene is used. For applications for which a majorprecision is required in order to avoid machining or in order to be ableto make ceramic coatings, normally, materials of major dimensionalstability, such as polypropylene of high density or wood components, areused. If available also a sheet with the desired shape can be used. Inthis case putty is employed in order to have a thick separator which iseasy to eliminate and which will be replaced afterwards by the thermallyprojected layer. A lot of materials and processes can be used in orderto obtain the model.

In comparison to metals, the major fragility of ceramics and highresistance polymers is a problem. If a die with a major toleranceregarding possible beats or falls should be obtained, the base materialshould be armoured. In case of low humidification cements (“low wateradmixture castables”), metals with a similar linear thermal expansioncoefficient to the base material should be used in order to avoid diecracks during the aging process. Even in the case of dies which areexposed to considerable temperature changes it is convenient to usemetals of a similar linear thermal expansion coefficient as the basematerial itself: iron or nickel (or any alloy having one of thosematerials as the base alloying element) for the concretes on the basesof porcelanates, and polymeric concrete, invar, constantan, tungsten ormolybdenum (or any alloy having one of those materials as the basealloying element) for cements with a high content of alumina and/orsilica.

The concretes are resistant against high compression loads, but theirresistance under tensile stress state is low. Almost all ceramics andmany high resistance polymers have a poor tensile strength. That is themain reason for the pieces of the present invention to be oftenarmoured. Another form of assuring that the piece is not exposed totensile stresses is the use of a hoop or external metallic compressionring or frame. The hoop or ring can also be used to prestress the rodsof the armouring. In this way, a more compressive tensional state in allpiece zones can be obtained which permits the fabrication of morecomplex geometries. For some applications though, the tensile mechanicalresistance of the low cost base material suffices. It is normally alsoadvantageous, especially when the working layer is applied by projectionor deposition of a metal, to allow the rods of the armouring to barelystick out of the low cost base material on the surfaces that are to beprojected to provide an extra anchorage to the projected or depositedcoating.

It is often interesting to provide the piece with a metallic base, aplate, frame or cast that can merely serve transportation ormontage/anchorage means, but can also provide resilience in the case ofaccidents, if the metallic plate, cast or frame is provided with spikesand bonded to the low cost material when casting or still fresh.

In the present invention, a metallic film often being of steel or othermetallic alloy (based on Fe, Ni, Co, Al, Mo, W or others) will be laidon the surface in order, to enhance the toughness in the working zone,to withstand the loading on the surface, to facilitate machining and,above all, to permit a good superficial finishing of the produced piece.Other materials than can be used for the surface working layer,providing the functionality required, are intermetallic compounds andtechnical ceramics (or any compound encompassing them like is the caseof hard metal). Projection and deposition methods are the bestcandidates to attain this metallic, intermetallic or technical ceramicsurface layer, but dipping into a melt or slurry or highly bondingparticle containing paints (like sol-gels) can also be employed,especially when a first projected/deposited intermediate layer isalready present. Thermal projection in one of its variants (regardlessof: the speed and means of acceleration/transportation of the projectedmaterial, the means of heating up the projected material or transportingfluid, the shape and size of the projected material [powder, otherparticles, rod, . . . ], whether the projected material softens orpartially melts, and whether it can be considered cold or hot spraying)is then a very suitable process to attain the superficial layer: coldspray projection, plasma projection (“Plasma spray”), HVOF projection(“High Velocity Oxyfuel Spray”), HFPD projection (“High Frequency PulseDetonation”), oxy-acetylene projection (“flame spray”), arc projection(“electric-arc spray”), or any other. The surface coating can also bemade by means of deposition of a fluid or a vapour (CVD—chemical VapourDeposition, PVD—Physiscal Vapour Deposition, EB—electron beambombardment, Ion Implantation, Plasma vapour deposition . . . ). Some ofthese processes can enhance some characteristics of theprojected/deposited layer and of the bonding quality if they arerealised in a controlled atmosphere chamber (at atmospheric pressure aswell as under pressure/depression). Any other process which permits theinsertion of a sufficiently thick layer and which provides a good unionbetween layer and basic material can be used such as cathode coating, ordipping into a melt of the desired material or a slurry containing thedesired material which is afterwards dried out, etched or burned toeliminate the carrier. In every case, the chosen technique depends onthe required properties at the interface with the base low cost ceramicand the working surface, which in turn depend on many process parametersand geometry conditionings. One very important aspect to be consideredare the residuals tensions stresses on the projected/deposited layerleft by the different possible techniques and which are very often inturn dependant on the thickness of the layer.

When constructing pieces with cylindrical symmetry, the superficiallayer can be applied as a solid body. For external cylindrical symmetrylike is the case in any type of axis and rolls, a metallic ring orsleeve can be used as working surface, which can be hooped by heating itup and thus expanding it, entering it with the aid of a press andletting it cool down and thus contracting against the base low costmaterial improving the anchorage. For internal cylindrical symmetry likeis the case of a cylinder hole in a motor block, or many others, ametallic liner can be used as working surface (it can also be pressuremounted and deep frozen and the low cost material heated up to improveanchorage).

As the desired functionality on the tool's surface is different in everyapplication, there are endless materials which can be applied assuperficial layer. In particular, steels with the desired hardness, butwith an enhanced mechanization, steels with lubricant or anti-adherentparticles, materials with an optimized tribologic behaviour and/ormaterials with an extreme wear resistance, as well as the aforementionedmaterials with specific, thermal, magnetic, electric, piezo- or piro-electric, or any other specific property can be projected/deposited. Inprinciple, every type of metal, metallic alloy, intermetallic compoundor ceramic or even compounds of them can be inserted.

When coating with a metal the adherence has a very remarkable influenceon the overall performance, therefore improving the adherence at theinterface is of great importance. To do so metallic fibres can beemployed. Normally the fibres are mixed with the low cost base materialand the cast together, unless the fibres are also desired in the body ofthe low cost base material to increase resistance in tensile stressstates, the fibres can be conducted to the surface, and preferablyoriented orthogonal to it, to have the biggest fibre pull-outresistance. This can be achieved by applying electric or magnetic fieldsto orient the fibres. For example some permanent magnets can be glued tothe shaping mould so that when filling the low cost material into whicha certain volume percentage of ferromagnetic fibres has beenincorporated, and during the vibration of the mix, the fibres can flowtowards the magnets aligning with the force lines which run fairlyperpendicular to the surface. To further increase the amount of metal onthe projecting surface, the piece can be shot penned or blasted tospread the metallic fibres onto the surface. The projected metal adheresespecially well to the metal of the base material, even more when thiscan plastically deform and also some diffusion bonding can be attainedif temperature is high enough during the projection or in a posteriortreatment.

When projecting a metal on a ceramic or polymer the bonding is mainly amechanical bonding, and thus it is better when the surface is somewhatrough, providing good anchorage points. When the base material hasmetallic fibres, the anchorage is also greatly improved if those fibresare activated prior to the thermal projection or deposition (activationis understood as removing all superficial oxides, to have a fibresurface which is as metallic as possible. For this purpose, usage ofsand blasting (with corundum, glass balls or micro-particles, . . . ) orshot penning (specially with metallic balls) to activate the metallicfibres and low cost base material surface are specially indicated, butany other method can be employed (grinding, polishing, roughening . . .).

The application of an intermediate layer can be considered in order toenhance the adherence of the surface working layer. Such layers couldbe, for instance, thermo stable layers which are humidity resistant andresistant against alkaline components (in order to avoid the corrosionof the metallic layer used in the inter phase). Such method is describedin JP4107251.

In order to enhance the adherence of the mechanically projected layer, asuperficial porosity can be produced in the base material by usingmodels which degas, by corrosion attack or others. A metallic grid canbe put on the model's surface. The concrete will be filled into themodel so that the grid is finally on the surface of the concrete tool.Also the metallic rods of the armouring can be fixed in the mould in away that they look out of the concrete item on each side on whichthermal projection/deposition will be realised, in particular, if thematerial to be employed as a surface working material, or supportintermediate layer sticks better on a metallic substrate than ceramic orpolymeric.

With some of the described thermal projection techniques, in particular,techniques in controlled atmosphere, densities of more than 99% can beobtained. If a higher surface density is required, a superficialdensification treatment can be realised by local fusion. A sufficientlycondensed energy source should be applied for local fusion such as laseror concentrated infra-red (HDIR-“High Density Infrared”). Any othermethod to increase density or even just superficial stress state can beemployed, whether they include melting (like welding), or just puremechanical action (like shot penning).

The projected/deposited surface material may require an integrated orsuperficial thermal treatment as for instance one or several annealingprocesses or a superficial treatment such as carbo-nitriding orsulfonizing, superficial tempering (by induction, laser, flame, etc.).Not every combination of low cost base material and surface materialspermits every treatment. If an elevated temperature is required for thesuperficial treatment, the compatibility of the linear thermal expansioncoefficients has to be taken into account and also the capacity of thebasic material to withstand the required temperature for the treatment.

For the transport and, in particular, in order to fix the tool in themachine, it is often interesting to have a zone in at the fixing side ofthe tool or piece which is easy to machine. In the present invention, aniron plate frame or melt can be installed for that purpose if requiredas aforementioned. Metallic profiles are also put in guiding zones whenthe low cost base material is cast so that they remain embedded in thestructure, but are easy to machine afterwards. If an anchoring plate orguiding zones are used they are normally inserted into the mould beforecasting the base material, or into the ceramic/polymer when still fresh.In general, such a plate or profiles have some welded metallic rods orspikes in order to enhance the anchorage to the low cost base material.

Although the present invention is especially well suited for thefabrication of drawing big dies, it can be used for the fabrication ofseveral tool types with considerable advantages. Some of these tools canbe: moulds for plastic injection, moulds for thermal shaping ofplastics, moulds for light metal injection, forging dies, dies for openforging, bending dies, cutting dies, etc. In those cases in which theworking temperature is higher, there are restrictions for the electionof the base material and the material for the thermal projection as thelinear thermal expansion coefficients must be compatible.

The present invention is also well suited for the fabrication of machinecomponents, whether mobile, actuator, sensory or structural. It allowsreducing weight in many instances, there is a big potential for costreduction when using the present invention, and also somefunctionalities, especially those involving complex patterns with aspecial functionality, are difficult to obtain in any othermanufacturing way. In fact almost any high solicited piece or partdemanding a complex functionality are susceptible of benefiting from thepresent invention.

Further embodiments of the invention are described in the attacheddependent claims.

EXAMPLES Example 1

In FIG. 2 an example of the present invention's application can be seen.It is a schematic representation of a drawing die. Normally, those diesare significantly more complex with blank-holder and lateral cams. Theschematic view in FIG. 2 a) corresponds to a drawing die which wasrealised according to the present invention. The image only focuses onthe melt support plate and on the hooped high resistance concrete itemwhich is coated by thermal projection HVOF (it has also been realizedwith cold spray on top of a first thin layer of HVOF projected metal,with equally satisfactory results and even thicker thicknessesattainable) with hot work tool steel and with additives which can bemachined easily. In principle, the difference in the working zonebetween this die and a die which was fabricated by the conventionalmethod can not be seen easily after machining. Only the compressionframe zone with the prestressed rods reveal the presence of concrete.This mould was obtained by following the following steps:

Mould fabrication in expanded polystyrene. A box with the negative ofthe tool form in its internal lower side.

Placement of the armouring in the mould, with rods which were inserted0.5 mm into the polystyrene mould in that area of the piece in whichafterwards metal will be projected by thermal projection. Some of thearmouring rods which are parallel to the working zone are inserted 0.5 min the polystyrene box in each side in order to be able to fix them inthe compression frame afterwards.

Filling out the cavern with a concrete of very high mechanicalresistance (250 MPa after ageing) and low humidity mainly on the basisof aluminium and silica oxide (“refractory low water admixturecastable”). An external vibration by means of a vibrating table and aninternal vibrating by a needle were realised during the filling outprocess.

curing of the full mould with plastics during 24 h

Extraction of the polystyrene model mould

Concrete drying and firing in order to eliminate the humidity, reactionat high temperature in a controlled atmosphere oven

Hooping of the concrete die with a demountable steel box with holes forthe long rods

Prestressing of the rods

Elimination of superficial dirt from the concrete die and activation ofthe surface with corundum sand blasting.

Thermal projection of a hot work steel layer which can be easilymachined

Final machining

FIG. 2 b) shows a schematic transversal cut in order to demonstrate thedifference to a conventional die. The basic transport plate and the diefixture (22) with the rods for the armouring of the concrete can be seenin the image. The armouring rods can also be seen (20). Some of them areprestressed (20A) with the help of the hoop (23). The used highresistance concrete (25) is a “low water admixture castable” on thebasis of alumina which was fired in a controlled atmosphere oven. Thearmouring rods enter the thermal projection layer (26). Finally, theimage shows the layer which has received a densification treatment bylocal laser fusion (30).

Example 2

A selective heating profiling roll was obtained with the presentinvention. The roll has embedded a conductive heating pattern on itsworking surface. This profiling roll was obtained by following thefollowing steps:

Mould fabrication in expanded polystyrene. An empty cylindrical cagewith the negative of the profiling contour was made.

Filling out the cavern with a 10% metallic fibre reinforcement highmechanical resistance concrete (HPC). An external vibration by means ofa vibrating table and an internal vibrating by a needle were realisedduring the filling out process.

Moisturized curing of the full mould with plastics during 24 h

Extraction of the polystyrene model mould

Concrete drying in order to eliminate the humidity and realizemechanical resistance.

Elimination of superficial dirt from the concrete die and activation ofthe surface and fibres with corundum sand blasting.

cold spray of a low conductivity titanium intermediate layer.

TiN PVD deposition to further increase isolation.

Masking, to reveal only the profile that has to have conductive heatingcapability.

Cu thermal projection.

elimination of masking

Machining the edges of the conductive heating profile from the projectedlayer.

Masking to obtain a thin isolation layer around the Cu profile

Alumina thermal projection.

elimination of masking.

masking of the already Cu and Al₂O₃ projected zones.

cold spraying of low thermal conductivity, high resistance Ni—Fe—Mnalloy.

removal of masking.

final machining.

Example 3

A hot stamping prototype die with integrated cooling was obtained. Thedie has some zones with high conductivity to realize high strength onthe produced components, and areas where conductivity is low, tofacilitate posterior cutting of the component. This die was obtained byfollowing the following steps:

Mould fabrication in expanded polystyrene. A box with the negative ofthe tool form in its internal lower side.

Placement of tubes with spikes on the Mould surface that corresponds tothe working surface, tubes are indented 0.5 mm into the polystyrene, thespikes are looking into the cavity away from the mould. Two independentcircuits are used, one for the areas where high heat extraction rate isdesirable and thus cooling will be performed, and one for areas wherelow heat extraction rates are desirable and thus tempering will beemployed.

Placement of the armouring in the mould, with rods which were inserted0.5 mm into the polystyrene mould in that area of the piece in whichafterwards metal will be projected by thermal projection. Some of thearmouring rods which are parallel to the working zone are inserted 0.5 min the polystyrene box in each side in order to be able to fix them inthe compression frame afterwards.

Filling out the cavern with a 10% metallic fibre reinforcement highmechanical resistance concrete (HPC). An external vibration by means ofa vibrating table and an internal vibrating by a needle were realisedduring the filling out process.

Moisturized curing of the full mould with plastics during 24 h(alternatively, curing by immersion in water after model removal)

Extraction of the polystyrene model mould

Concrete drying in order to eliminate the humidity and realizemechanical resistance.

Elimination of superficial dirt from the concrete die and activation ofthe surface, tubes and fibres with corundum sand blasting.

Hooping of the concrete die with a demountable steel box with holes forthe long rods

Prestressing of the rods.

HVOF thermal spraying of a 0.5 mm thick molybdenum or aluminium layer.

Masking of the areas where high heat extraction rate is desired.

Cold spray with a thick (20 mm) Ti low heat conductivity alloy of theareas corresponding to component zones to be cut, or areas where thecomponent has to have high deformability and thus low heat extractionrate in the tooling is desired (tempering circuit zone).

Elimination of the masking.

Masking of the already projected low conductivity zones.

Cold spray of a high conductivity molybdenum alloy or aluminium thick(20 mm) layer which can be easily machined.

Removal of the masking.

Final machining.

1. Piece or tool, wherein the base material is a concrete or low wateradmixture castable, with a mechanical resistance higher than 200 MPa. 2.Piece or tool according to claim 1, wherein the base material is aconcrete or low water admixture castable, with a mechanical resistancehigher than 250 MPa.
 3. Piece or tool according to claim 1, wherein thematerial is at least partially coated with a metal, an inter-metalliccompound or a technical ceramic.
 4. Piece or tool according to claim 3,wherein the coating includes a thermal projection coating.
 5. Piece ortool according to claim 1, wherein a portion of the arid of the high orultrahigh resistance concrete (HPC or UHPC) is at least partly replacedby metallic particles.
 6. Piece or tool according to claim 1, wherein aportion of the cement of the high or ultrahigh resistance concrete (HPCor UHPC) is replaced by metallic nanopowders.
 7. Piece or tool accordingto claim 1, wherein the base material is internally armoured withmetallic parts.
 8. Piece or tool according to claim 1, wherein the pieceor tool is hopped by means of a compression ring to improve tensilestress resistance of the resulting part.
 9. Piece or tool according toclaim 1, further comprising tubes superficially or subsuperficiallyplaced in the base material, conferring a cooling/heating functionalityto the piece or tool when a fluid is circulated through the tubes. 10.Piece or tool according to claim 1, which is a tool for the forming ofplastics, sheet forming or alloy die casting.
 11. Piece according toclaim 1, which is a structural component, machine bench or othercomponent.